U.S. patent application number 13/380658 was filed with the patent office on 2012-04-19 for asymmetric and/or low-symmetric fluorine-containing phosphate for non-aqueous electrolyte solution.
This patent application is currently assigned to TOSOH F-TECH, INC.. Invention is credited to Masahiro Aoki, Hisao Eguchi, Kentaro Kono, Hideyuki Mimura, Kotaro Sakoda.
Application Number | 20120094190 13/380658 |
Document ID | / |
Family ID | 43544122 |
Filed Date | 2012-04-19 |
United States Patent
Application |
20120094190 |
Kind Code |
A1 |
Mimura; Hideyuki ; et
al. |
April 19, 2012 |
ASYMMETRIC AND/OR LOW-SYMMETRIC FLUORINE-CONTAINING PHOSPHATE FOR
NON-AQUEOUS ELECTROLYTE SOLUTION
Abstract
As to a fluorine-containing phosphate used to impart flame
retardancy to an electrolyte solution for a non-aqueous secondary
battery, a fluorine-containing phosphate having high flame
retardancy and providing high battery performance such as high-rate
charge-discharge characteristics, and a method for manufacturing
the same are provided. Also provided are a non-aqueous electrolyte
solution and a non-aqueous secondary battery each containing the
fluorine-containing phosphate. Further a fluorine-containing
phosphate having a high ability to dissolve an electrolyte and
capable of providing the composition of a safer electrolyte
solution is provided. The fluorine-containing phosphate for a
non-aqueous electrolyte solution is represented by the general
formula (1) ##STR00001## (wherein R represents an alkyl group
having 1 to 10 carbon atoms or a fluorine-containing alkyl group
having 1 to 10 carbon atoms, A and B are different from each other
and each represent a hydrogen atom or a fluorine atom, and n and m
each independently represent an integer from 1 to 8) and contains
fluorine atoms in a weight ratio of 30% or higher.
Inventors: |
Mimura; Hideyuki;
(Yamaguchi, JP) ; Kono; Kentaro; (Yamaguchi,
JP) ; Eguchi; Hisao; (Yamaguchi, JP) ; Sakoda;
Kotaro; (Yamaguchi, JP) ; Aoki; Masahiro;
(Yamaguchi, JP) |
Assignee: |
TOSOH F-TECH, INC.
Shunan-shi, Yamaguchi
JP
|
Family ID: |
43544122 |
Appl. No.: |
13/380658 |
Filed: |
July 30, 2010 |
PCT Filed: |
July 30, 2010 |
PCT NO: |
PCT/JP2010/004851 |
371 Date: |
December 23, 2011 |
Current U.S.
Class: |
429/324 ;
429/200; 558/204; 558/97 |
Current CPC
Class: |
H01M 10/052 20130101;
Y02E 60/10 20130101; H01M 10/4235 20130101; Y02T 10/70 20130101;
H01M 10/0569 20130101; H01M 10/0525 20130101 |
Class at
Publication: |
429/324 ;
429/200; 558/204; 558/97 |
International
Class: |
H01M 10/056 20100101
H01M010/056; C07F 9/141 20060101 C07F009/141 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 4, 2009 |
JP |
2009-181436 |
Dec 2, 2009 |
JP |
2009-274816 |
Claims
1. A fluorine-containing phosphate for a non-aqueous electrolyte
solution, being represented by the general formula (1),
##STR00006## (wherein R represents an alkyl group having 1 to 10
carbon atoms or a fluorine-containing alkyl group having 1 to 10
carbon atoms, A and B are different from each other and each
represent a hydrogen atom or a fluorine atom, and n and m each
independently represent an integer from 1 to 8) and containing
fluorine atoms in a weight ratio of 30% or higher.
2. The fluorine-containing phosphate for a non-aqueous electrolyte
solution according to claim 1, characterized in that in the general
formula (1) n and m are each independently an integer from 1 to 4,
and R is an alkyl group having 1 to 4 carbon atoms or a
fluorine-containing alkyl group having 1 to 4 carbon atoms.
3. The fluorine-containing phosphate for a non-aqueous electrolyte
solution according to claim 1, characterized in that in the general
formula (1) n and m are each independently an integer from 1 to 4,
and R is one selected from a methyl group, an ethyl group, a
2,2-difluoroethyl group, a 2,2,2-trifluoroethyl group, a
2,2,3,3-tetrafluoropropyl group, and a 2,2,3,3,3-pentafluoropropyl
group.
4. The fluorine-containing phosphate for a non-aqueous electrolyte
solution according to claim 1, wherein the compound represented by
the general formula (1) is bis(2,2,2-trifluoroethyl)
2,2,3,3-tetrafluoropropyl phosphate.
5. The fluorine-containing phosphate for a non-aqueous electrolyte
solution according to claim 1, wherein the compound represented by
the general formula (1) is bis(2,2,3,3-tetrafluoropropyl)
2,2,2-trifluoroethyl phosphate.
6. The fluorine-containing phosphate for a non-aqueous electrolyte
solution according to claim 1, wherein the compound represented by
the general formula (1) is bis(2,2,2-trifluoroethyl)
2,2-difluoroethyl phosphate.
7. The fluorine-containing phosphate for a non-aqueous electrolyte
solution according to claim 1, wherein the compound represented by
the general formula (1) is methyl 2,2,3,3-tetrafluoropropyl
2,2,2-trifluoroethyl phosphate.
8. A non-aqueous electrolyte solution containing the
fluorine-containing phosphate according to claim 1.
9. A non-aqueous electrolyte solution containing the
fluorine-containing phosphate according to claim 1 and a lithium
salt.
10. A non-aqueous electrolyte solution containing a lithium salt
and an organic solvent containing the fluorine-containing phosphate
according to claim 1 in a weight ratio of 3 to 60%.
11. A non-aqueous electrolyte solution containing a lithium salt
and an organic solvent containing the fluorine-containing phosphate
according to claim 1 in a weight ratio of 5 to 40%.
12. A non-aqueous secondary battery in which the non-aqueous
electrolyte solution according to claim 8 is used.
13. A method for manufacturing a fluorine-containing phosphate
represented by the general formula (1) through a three-step
reaction, the three-step reaction including the steps of: 1)
reacting phosphorus trichloride with t-butanol, a
fluorine-containing alcohol represented by the general formula (2)
A(CF.sub.2).sub.nCH.sub.2OH (2) (wherein A is a hydrogen atom or a
fluorine atom, and n is an integer from 1 to 8), and an alcohol
represented by the general formula (3) ROH (3) (wherein R is an
alkyl group having 1 to 10 carbon atoms or a fluorine-containing
alkyl group having 1 to 10 carbon atoms) to produce a
fluorine-containing phosphite represented by the general formula
(4) ##STR00007## (wherein A, n, and R are as defined above), 2)
reacting the fluorine-containing phosphite represented by the
general formula (4) with molecular chlorine to produce a
fluorine-containing chlorophosphate represented by the general
formula (5) ##STR00008## (wherein A, n, and R are as defined
above), and 3) reacting the fluorine-containing chlorophosphate
represented by the general formula (5) with a fluorine-containing
alcohol represented by the general formula (6)
B(CF.sub.2).sub.mCH.sub.2OH (6) (wherein B represents a hydrogen
atom or a fluorine atom, provided that B is different from A in the
formula (2), and m represents an integer from 1 to 8) in the
presence of a Lewis acid catalyst to thereby produce the
fluorine-containing phosphate represented by the general formula
(1), the method characterized in that, in at least the step 1), a
solvent is used in an amount of 0 to 1 times the total amount of
raw materials in a weight ratio.
14. An asymmetric fluorine-containing phosphate, wherein in the
general formula (1) R is different from CH.sub.2(CF.sub.2).sub.nA
and from CH.sub.2(CF.sub.2).sub.mB.
15. The asymmetric fluorine-containing phosphate according to claim
14, wherein the fluorine-containing phosphate represented by the
general formula (1) is methyl 2,2,3,3-tetrafluoropropyl
2,2,2-trifluoroethyl phosphate.
Description
TECHNICAL FIELD
[0001] The present invention relates to a fluorine-containing
phosphate used as a flame retardant for a non-aqueous electrolyte
solution. More particularly, the invention relates to a
fluorine-containing phosphate having a specific structure and
providing excellent physical properties and characteristics as a
non-aqueous electrolyte solution, to a method for manufacturing the
same, and to a non-aqueous electrolyte solution and a non-aqueous
secondary battery each containing the fluorine-containing
phosphate.
BACKGROUND ART
[0002] Non-aqueous secondary batteries have a high power density
and a high energy density and are widely used as power sources of
mobile phones and personal computers. Such non-aqueous secondary
batteries produce clean energy with low carbon dioxide emissions,
and active research on their applications to power sources for
power storage and power sources for electric automobiles is
recently being conducted.
[0003] Known examples of the non-aqueous secondary battery include
lithium secondary batteries, lithium ion secondary batteries,
magnesium secondary batteries, and magnesium ion secondary
batteries. For example, in lithium secondary batteries and lithium
ion secondary batteries, a material containing a lithium-containing
transition metal oxide as a main component is used for a positive
electrode. Further, metal lithium or a lithium alloy is used for a
negative electrode. Or alternatively, for example, a material
containing a carbonaceous material typified by graphite as a main
component is used for the negative electrode. These batteries are
referred to as lithium secondary batteries and lithium ion
secondary batteries respectively. The positive and negative
electrodes are provided with a separator interposed therebetween,
and the space between the positive and negative electrodes is
filled with a non-aqueous electrolyte solution serving as a medium
for migration of Li ions. A solution obtained by dissolving an
electrolyte such as lithium hexafluorophosphate (LiPF.sub.6) in a
high-permittivity organic solvent such as ethylene carbonate or
dimethyl carbonate is widely used as the non-aqueous electrolyte
solution. However, such an organic solvent is volatile and
flammable and is a solvent classified as a flammable material.
Therefore, there is a demand for a nonflammable non-aqueous
electrolyte solution for use particularly in large-scale
non-aqueous secondary battery applications such as power sources
for power storage and power sources for electric automobiles, and
attention is given to a technology that uses a flame retardant or
self-extinguishing non-aqueous electrolyte solution.
[0004] For the purpose of imparting flame retardancy to a
non-aqueous electrolyte solution, it is contemplated to add a
phosphate known as a flame retardant for resin materials (Patent
Literatures 1 and 2). Particularly, a fluorine-containing phosphate
having a fluorine atom on its ester side chain is known to have
high flame retardancy and is a promising material because such a
phosphate provides a wide electrolyte solution composition range in
which both the battery function and flame retardancy can be
obtained (Non-Patent Literature 1 and Patent Literatures 3, 4, 5,
and 6).
[0005] When a non-aqueous secondary battery is used as, for
example, the power source of an electric automobile, the battery is
required not only to be safe but also to have high battery
performance. Therefore, the use of a fluorine-containing phosphate
having an improved structure is being contemplated. In Patent
Literatures 3 and 4, the use of a fluorine-containing phosphate in
which the structures at the terminal ends of all the ester groups
are CF.sub.3 is contemplated. In Patent Literatures 5 and 6, the
use of a fluorine-containing phosphate in which the structures at
the terminal ends of all the ester groups are CF.sub.2H is
contemplated. However, a battery containing any of the above
fluorine-containing phosphates does not have sufficient battery
performance such as high-rate charge-discharge characteristics.
[0006] To impart higher flame retardancy to a battery, it is
desirable that the amount of a low-flash point solvent such as a
chain carbonate contained in the electrolyte solution be reduced or
such a low-flash point solvent be not used. In such a case, the
ability of the fluorine-containing phosphate to dissolve the
electrolyte is important to maintain the concentration of the
electrolyte in the electrolyte solution. However, the
fluorine-containing phosphates in Patent Literatures 3, 4, 5, and 6
are not satisfactory from this point of view.
[0007] An example of the synthesis of a fluorine-containing
phosphate having both CF.sub.3 and CF.sub.2H as the structures of
the terminal ends of ester groups in one molecule has been reported
in Non-Patent Literature 2. However, the basic properties, such as
viscosity, permittivity, and surface tension required for a
non-aqueous electrolyte solution, of the fluorine-containing
phosphate having the above specific structure have not been
reported, and there are no known non-aqueous electrolyte solutions
and non-aqueous secondary batteries that use the above
fluorine-containing phosphate.
[0008] In addition, no example of the synthesis of an asymmetric
fluorine-containing phosphate that has both CF.sub.3 and CF.sub.2H
as the structures of the terminal ends of ester groups in one
molecule and in which the structures of the three ester side chains
are different from each other has been reported.
CITATION LIST
Patent Literature
[0009] Patent Literature 1: Japanese Patent Application Laid-Open
No. Hei 8-22839 [0010] Patent Literature 2: Japanese Patent
Application Laid-Open No. Hei 11-260401 [0011] Patent Literature 3:
Japanese Patent Application Laid-Open No. Hei 8-088023 [0012]
Patent Literature 4: Japanese Patent Application Laid-Open No.
2007-258067 [0013] Patent Literature 5: Japanese Patent Application
Laid-Open No. 2007-141760 [0014] Patent Literature 6: Japanese
Patent Application Laid-Open No. 2008-21560
Non Patent Literature
[0014] [0015] Non-Patent Literature 1: J. Electrochem. Soc., 149,
A1079 (2002) [0016] Non-Patent Literature 2: J. Fluor. Chem., 106,
153 (2000)
SUMMARY OF INVENTION
Technical Problems
[0017] The present invention has been made in view of the foregoing
problems. Accordingly, it is an object to provide a
fluorine-containing phosphate used for an electrolyte solution for
a non-aqueous secondary battery, particularly a fluorine-containing
phosphate having high flame retardancy and providing high battery
performance such as high-rate charge-discharge characteristics, a
method for manufacturing the same, and a non-aqueous electrolyte
solution and a non-aqueous secondary battery that contain the
fluorine-containing phosphate.
[0018] It is another object to provide a fluorine-containing
phosphate having a high ability to dissolve an electrolyte and
capable of providing the composition of a safer electrolyte
solution.
Solution to Problem
[0019] The present inventors have conducted extensive studies to
solve the foregoing problems and found a fluorine-containing
phosphate having a specific structure with characteristics suitable
for a non-aqueous electrolyte solution, a method for manufacturing
the same with a high yield, and a high-performance non-aqueous
electrolyte solution and a high-performance non-aqueous secondary
battery each containing the fluorine-containing phosphate, and thus
the present invention has been completed. Therefore, the gist of
the present invention is as follows.
[0020] (1) A fluorine-containing phosphate for a non-aqueous
electrolyte solution, being represented by the general formula
(1)
##STR00002##
(wherein R represents an alkyl group having 1 to 10 carbon atoms or
a fluorine-containing alkyl group having 1 to 10 carbon atoms, A
and B are different from each other and each represent a hydrogen
atom or a fluorine atom, and n and m each independently represent
an integer from 1 to 8) and containing fluorine atoms in a weight
ratio of 30% or higher.
[0021] (2) The fluorine-containing phosphate for a non-aqueous
electrolyte solution according to (1), characterized in that in the
general formula (1) n and m are each independently an integer from
1 to 4, and R is an alkyl group having 1 to 4 carbon atoms or a
fluorine-containing alkyl group having 1 to 4 carbon atoms.
[0022] (3) The fluorine-containing phosphate for a non-aqueous
electrolyte solution according to (1), characterized in that in the
general formula (1) n and m are each independently an integer from
1 to 4, and R is one selected from a methyl group, an ethyl group,
a 2,2-difluoroethyl group, a 2,2,2-trifluoroethyl group, a
2,2,3,3-tetrafluoropropyl group, and a 2,2,3,3,3-pentafluoropropyl
group.
[0023] (4) The fluorine-containing phosphate for a non-aqueous
electrolyte solution according to (1), wherein the compound
represented by the general formula (1) is bis(2,2,2-trifluoroethyl)
2,2,3,3-tetrafluoropropyl phosphate.
[0024] (5) The fluorine-containing phosphate for a non-aqueous
electrolyte solution according to (1), wherein the compound
represented by the general formula (1) is
bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl phosphate.
[0025] (6) The fluorine-containing phosphate for a non-aqueous
electrolyte solution according to (1), wherein the compound
represented by the general formula (1) is bis(2,2,2-trifluoroethyl)
2,2-difluoroethyl phosphate.
[0026] (7) The fluorine-containing phosphate for a non-aqueous
electrolyte solution according to (1), wherein the compound
represented by the general formula (1) is methyl
2,2,3,3-tetrafluoropropyl 2,2,2-trifluoroethyl phosphate.
[0027] (8) A non-aqueous electrolyte solution containing the
fluorine-containing phosphate according to any one of (1) to
(7).
[0028] (9) A non-aqueous electrolyte solution containing the
fluorine-containing phosphate according to any one of (1) to (7)
and a lithium salt.
[0029] (10) A non-aqueous electrolyte solution containing a lithium
salt and an organic solvent containing the fluorine-containing
phosphate according to any one of (1) to (7) in a weight ratio of 3
to 60%.
[0030] (11) A non-aqueous electrolyte solution containing a lithium
salt and an organic solvent containing the fluorine-containing
phosphate according to any one of (1) to (7) in a weight ratio of 5
to 40%.
[0031] (12) A non-aqueous secondary battery in which the
non-aqueous electrolyte solution according to any one of (8) to
(11) is used.
[0032] (13) A method for manufacturing a fluorine-containing
phosphate represented by the general formula (1) through a
three-step reaction, the three-step reaction including the steps
of
[0033] 1) reacting phosphorus trichloride with t-butanol, a
fluorine-containing alcohol represented by the general formula
(2)
A(CF.sub.2).sub.nCH.sub.2OH (2)
(wherein A is a hydrogen atom or a fluorine atom, and n is an
integer from 1 to 8), and an alcohol represented by the general
formula (3)
ROH (3)
(wherein R is an alkyl group having 1 to 10 carbon atoms or a
fluorine-containing alkyl group having 1 to 10 carbon atoms) to
produce a fluorine-containing phosphite represented by the general
formula (4)
##STR00003##
(wherein A, n, and R are as defined above),
[0034] 2) reacting the fluorine-containing phosphite represented by
the general formula (4) with molecular chlorine to produce a
fluorine-containing chlorophosphate represented by the general
formula (5)
##STR00004##
(wherein A, n, and R are as defined above), and
[0035] 3) reacting the fluorine-containing chlorophosphate
represented by the general formula (5) with a fluorine-containing
alcohol represented by the general formula (6)
B(CF.sub.2).sub.mCH.sub.2OH (6)
(wherein B represents a hydrogen atom or a, fluorine atom, provided
that B is different from A in the formula (2), and m represents an
integer from 1 to 8) in the presence of a Lewis acid catalyst to
thereby produce the fluorine-containing phosphate represented by
the general formula (1), wherein, in at least the step 1), a
solvent is used in an amount of 0 to 1 times the total amount of
raw materials in a weight ratio.
[0036] (14) An asymmetric fluorine-containing phosphate, wherein,
in the general formula (1), R is different from
CH.sub.2(CF.sub.2).sub.nA and from CH.sub.2 (CF.sub.2).sub.mB.
[0037] (15) The asymmetric fluorine-containing phosphate according
to (14), wherein the fluorine-containing phosphate represented by
the general formula (1) is methyl 2,2,3,3-tetrafluoropropyl
2,2,2-trifluoroethyl phosphate.
Advantageous Effects of Invention
[0038] According to the present invention, a fluorine-containing
phosphate for a non-aqueous electrolyte solution that has a
specific structure proving high flame retardancy and high-battery
performance such as high-rate charge-discharge characteristics and
a method of manufacturing the same are provided. A non-aqueous
electrolyte solution and a non-aqueous secondary battery each
containing the fluorine-containing phosphate and having improved
performance are also provided.
[0039] In addition, a fluorine-containing phosphate having a high
ability to dissolve an electrolyte and capable of providing the
composition of a safer electrolyte solution is provided.
BRIEF DESCRIPTION OF DRAWING
[0040] FIG. 1 is a schematic cross-sectional view of a non-aqueous
secondary battery used in Examples 18 to 26 and Comparative
Examples 6 to 8.
DESCRIPTION OF EMBODIMENTS
[0041] The present invention will next be described in more
detail.
[0042] A fluorine-containing phosphate of the present invention for
a non-aqueous electrolyte solution is represented by the general
formula (1) above. More specifically, at least one of the ester
side chains has a terminal CF.sub.3 structure, and at least one has
a terminal CF.sub.2H structure. The structures of the three ester
side chains are different from each other, or two of them are the
same. The former is referred to as an asymmetric
fluorine-containing phosphate because it has no symmetry plane, and
the latter is referred to as a low-symmetric fluorine-containing
phosphate because it has only one symmetry plane. In addition, the
fluorine-containing phosphate of the present invention contains
fluorine atoms in a weight ratio of 30% or higher. A ratio of
fluorine atoms in the fluorine-containing phosphate of less than 30
wt % is not preferred because the flame retardancy of a non-aqueous
electrolyte solution or non-aqueous secondary battery containing
the fluorine-containing phosphate is not satisfactory.
[0043] Since the fluorine-containing phosphate has any of the above
specific structures, it can provide not only high flame retardancy
but also good characteristics as a non-aqueous electrolyte
solution. Accordingly, a non-aqueous secondary battery using the
fluorine-containing phosphate has high performance such as
high-rate charge-discharge characteristics.
[0044] Since the fluorine-containing phosphate has any of the above
specific structures, its ability to dissolve an electrolyte is
significantly improved, and the composition of a highly safe
electrolyte solution can be provided.
[0045] In the general formula (1), n and m are each independently
an integer from 1 to 8. Particularly, n and m are preferably 1 to
4. R is an alkyl group having 1 to 10 carbon atoms or a
fluorine-containing alkyl group having 1 to 10 carbon atoms.
Particularly, R is preferably an alkyl group having 1 to 4 carbon
atoms or a fluorine-containing alkyl group having 1 to 4 carbon
atoms. More preferably, R is one selected from a methyl group, an
ethyl group, a 2,2-difluoroethyl group, a 2,2,2-trifluoroethyl
group, a 2,2,3,3-tetrafluoropropyl group, and a
2,2,3,3,3-pentafluoropropyl group.
[0046] Examples of such a fluorine-containing phosphate include
bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate,
bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl phosphate,
bis(2,2,2-trifluoroethyl) 2,2,3,3,4,4,5,5-octafluoropentyl
phosphate, bis(2,2,2-trifluoroethyl)
2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl phosphate,
bis(2,2,2-trifluoroethyl)
2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononyl phosphate,
bis(2,2-difluoroethyl) 2,2,2-trifluoroethyl phosphate,
bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl phosphate,
bis(2,2,3,3-tetrafluoropropyl) 2,2,3,3,3-pentafluoropropyl
phosphate, bis(2,2,3,3-tetrafluoropropyl)
2,2,3,3,4,4,5,5,5-nonafluoropentyl phosphate,
bis(2,2,3,3-tetrafluoropropyl)
2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptyl phosphate,
bis(2,2,3,3-tetrafluoropropyl)
2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononyl phosphate,
methyl 2,2-difluoroethyl 2,2,2-trifluoroethyl phosphate, methyl
2,2,3,3-tetrafluoropropyl-2,2,2-trifluoroethyl phosphate, ethyl
2,2,3,3-tetrafluoropropyl 2,2,2-trifluoroethyl phosphate, hexyl
2,2,3,3-tetrafluoropropyl 2,2,2-trifluoroethyl phosphate, octyl
2,2,3,3-tetrafluoropropyl 2,2,2-trifluoroethyl phosphate, and decyl
2,2,3,3-tetrafluoropropyl 2,2,2-trifluoroethyl phosphate. Of these
fluorine-containing phosphates, bis(2,2,2-trifluoroethyl)
2,2,3,3-tetrafluoropropyl phosphate, bis(2,2,3,3-tetrafluoropropyl)
2,2,2-trifluoroethyl phosphate, bis(2,2,2-trifluoroethyl)
2,2-difluoroethylphosphate, and methyl 2,2,3,3-tetrafluoropropyl
2,2,2-trifluoroethyl phosphate are particularly preferred in terms
of battery performance.
[0047] It is desirable that these fluorine-containing phosphates be
high purity phosphates. Particularly, it is desirable that the
amounts of protic compounds such as water, acids, and alcohols be
less than 30 ppm. A single one of or a mixture of at least one of
these fluorine-containing phosphates may be used for anon-aqueous
electrolyte solution.
[0048] A description will next be given of a method for
manufacturing the fluorine-containing phosphate having any of the
above specific structures. The fluorine-containing phosphate of the
present invention represented by the general formula (1) can be
synthesized using, for example, any of methods described in J.
Fluor. Chem., 113, 65 (2002) and J. Fluor. Chem., 106, 153 (2000),
i.e., according to the scheme 1.
##STR00005##
[0049] In the above scheme, when the alcohol represented by the
general formula (3) is the same as any one of the
fluorine-containing alcohols represented by the general formulas
(2) and (6), it is a synthesis method of a low-symmetric
fluorine-containing phosphate. When the alcohol represented by the
general formula (3) is different from the fluorine-containing
alcohols represented by the general formulas (2) and (6), it is a
synthesis method of an asymmetric fluorine-containing
phosphate.
[0050] In a first step, A in the fluorine-containing alcohol
represented by the general formula (2) represents a hydrogen atom
or a fluorine atom, and n represents an integer from 1 to 8.
Examples of such a fluorine-containing alcohol include
2,2-difluoroethanol 2,2,2-trifluoroethanol,
2,2,3,3-tetrafluoropropanol, 2,2,3,3,3-pentafluoropropanol,
2,2,3,3,4,4,5,5-octafluoropentanol,
2,2,3,3,4,4,5,5,5-nonafluoropentanol,
2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptanol,
2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptanol,
2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononanol, and
2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanol. The
alcohol represented by the general formula (3) is a fluorine-free
or fluorine-containing alcohol having 1 to 10 carbon atoms and is
the same as one of the fluorine-containing alcohols represented by
the general formulas (2) and (6) or different from them. Examples
of the alcohol represented by the general formula (3) include
methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol,
t-butanol, n-hexanol, n-octanol, n-decanol, 2,2-di fluoroethanol,
2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoropropanol,
2,2,3,3,3-pentafluoropropanol, 2,2,3,3,4,4,5,5-octafluoropentanol,
2,2,3,3,4,4,5,5,5-nonafluoropentanol,
2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptanol,
2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptanol,
2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononanol, and
2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanol.
[0051] In the first step, a solvent may be used. The desired
solvent is an aprotic solvent, and examples of the aprotic solvent
include: alkanes such as hexane and heptane; aromatic hydrocarbons
such as benzene and toluene; halogenated hydrocarbons such as
dichloromethane and chloroform; ethers such as diethyl ether and
tetrahydrofuran; ketones such as acetone and methyl ethyl ketone;
esters such as ethyl acetate and butyl acetate; nitriles such as
acetonitrile and propionitrile; and amides such as
dimethylformamide and dimethylacetamide. Particularly, the present
invention is characterized in that, at least in the first step, the
amount of the solvent used is 0 to 1 times the total amount of the
raw materials including phosphorus trichloride, t-butanol, the
fluorine-containing alcohol represented by the general formula (2),
and the alcohol represented by the general formula (3) in a weight
ratio, so that the fluorine-containing phosphate represented by the
general formula (1) is obtained with a high yield.
[0052] In the first step, the amount of t-butanol used is 0.5 to 2
times the amount of phosphorus trichloride in a molar ratio, and
the amounts of the fluorine-containing alcohol represented by the
general formula (2) and the alcohol represented by the general
formula (3) are each 0.5 to 4 times the amount of phosphorus
trichloride in a molar ratio. The order of mixing the raw materials
is not specifically limited. Generally, phosphorus trichloride is
mixed with t-butanol, and then the alcohols represented by the
general formulas (2) and (3) are added to the mixture. The reaction
temperature is -20 to 100.degree. C., and the reaction time is 10
minutes to 100 hours. After completion of the reaction, the
produced fluorine-containing phosphite represented by the general
formula (4) may be purified or not and then is used in a second
step.
[0053] In the second step, the fluorine-containing phosphite
represented by the general formula (4) and produced in the first
step is reacted with molecular chlorine. The same solvent as that
used in the first step may also be used in this step. The amount of
the solvent used is preferably 0 to 1 times the total amount of the
raw materials including the fluorine-containing phosphite
represented by the general formula (4) and the molecular chlorine
in a weight ratio. The amount of the molecular chlorine used is 0.8
to 2 times the amount of the fluorine-containing phosphite
represented by the general formula (4) in a molar ratio. The
reaction temperature is -20 to 100.degree. C., and the reaction
time is 10 minutes to 100 hours. After completion of the reaction,
the produced fluorine-containing chlorophosphate represented by the
general formula (5) may be purified or not and then is used in a
third step.
[0054] In the third step, the fluorine-containing chlorophosphate
represented by the general formula (5) and produced in the second
step is reacted with the fluorine-containing alcohol represented by
the general formula (6) in the presence of a Lewis acid catalyst.
The same solvent as that used in the first step may also be used in
this step. The amount of the solvent used is preferably 0 to 1
times the total amount of the raw materials including the
fluorine-containing chlorophosphate represented by the general
formula (5), the Lewis acid, and the fluorine-containing alcohol
represented by the general formula (6) in a weight ratio. It is
desirable that the Lewis acid catalyst be a metal halide, and
examples thereof include lithium chloride, magnesium chloride,
calcium chloride, boron chloride, aluminum chloride, iron chloride,
and titanium chloride. In the fluorine-containing alcohol
represented by the general formula (6), m in the formula represents
an integer from 1 to 8, and B represents a fluorine atom or a
hydrogen atom. When A in the general formula (2) is a fluorine
atom, B in the general formula (6) is a hydrogen atom, and examples
of the fluorine-containing alcohol represented by the general
formula (6) include 2,2-difluoroethanol,
2,2,3,3-tetrafluoropropanol, 2,2,3,3,4,4,5,5-octafluoropentanol,
2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptanol, and
2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononanol. When A in
the general formula (2) is a hydrogen atom, B in the general
formula (6) is a fluorine atom, and examples of the
fluorine-containing alcohol represented by the general formula (6)
include 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoropropanol,
2,2,3,3,4,4,5,5,5-nonafluoropentanol,
2,2,3,3,4,4,5,5,6,6,7,7,7-tridecafluoroheptanol, and
2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-heptadecafluorononanol. The
amount of the Lewis acid catalyst used is 0.01 to 0.5 times the
amount of the fluorine-containing chlorophosphate represented by
the general formula (5) in a molar ratio. The amount of the
fluorine-containing alcohol represented by the general formula (6)
used is 0.5 to 2 times the amount of the fluorine-containing
chlorophosphate represented by the general formula (5) in a molar
ratio. The reaction temperature is -20 to 200.degree. C., and the
reaction time is 10 minutes to 100 hours.
[0055] After completion of the reaction, the produced
fluorine-containing phosphate represented by the general formula
(1) can be isolated by any known method such as extraction or
distillation.
[0056] A description will next be given of a non-aqueous
electrolyte solution containing the fluorine-containing phosphate
having any of the above specific structures of the present
invention and a non-aqueous secondary battery containing the
non-aqueous electrolyte solution.
[0057] The above-described fluorine-containing phosphate may be
used alone as a solvent for an electrolyte or used as a mixture
with another organic solvent. In such a case, examples of the
organic solvent include: cyclic carbonates such as propylene
carbonate, ethylene carbonate, butylene carbonate, chloroethylene
carbonate, and fluoroethylene carbonate; cyclic esters such as
.gamma.-butyrolactone, .gamma.-valerolactone, and propiolactone;
chain carbonates such as dimethyl carbonate, diethyl carbonate,
ethyl methyl carbonate, diphenyl carbonate, and
bis(2,2,2-trifluoroethyl)carbonate; chain esters such as methyl
acetate, methyl butyrate, and trifluoro ethyl acetate; ethers such
as diisopropyl ether, tetrahydrofuran, dioxolane, dimethoxyethane,
diethoxyethane, methoxyethoxyethane, perfluorobutylmethyl ether,
2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, and
2,2,3,3-tetrafluoropropyl-1,1,2,2-tetrafluoroethyl ether; and
nitriles such as acetonitrile and benzonitrile. These may be used
alone or as a mixture of two or more. Particularly, when the
fluorine-containing phosphate is mixed with any of these solvents,
the amount of the fluorine-containing phosphate added is preferably
3 to 60 percent by weight with respect to the amount of the organic
solvent, and more preferably 5 to 40 percent by weight. When the
added amount in the weight ratio is less than 3%, the flame
retardant effect of the electrolyte solution is not satisfactory.
The larger the amount added, the higher the flame retardant effect.
However, when the added amount in the weight ratio is more than
60%, the battery performance may deteriorate.
[0058] As an electrolyte salt used to constitute the non-aqueous
electrolyte solution, lithium salts, magnesium salts, and the like
can be used because they are stable over a wide potential range.
Examples of such an electrolyte salt include LiBF.sub.4,
LiPF.sub.6, LiClO.sub.4, LiCF.sub.3SO.sub.3,
LiN(CF.sub.3SO.sub.2).sub.2, LiN(C.sub.2F.sub.6SO.sub.2).sub.2,
LiC(CF.sub.3SO.sub.2).sub.3, Mg(ClO.sub.4).sub.2,
Mg(CF.sub.3SO.sub.3).sub.2, and
Mg(N(CF.sub.3SO.sub.2).sub.2).sub.2. These may be used alone or as
a mixture of two or more. To obtain good high-rate charge-discharge
characteristics of the battery, the concentration of the
electrolyte salt in the non-aqueous electrolyte solution is
preferably in the range of 0.5 to 2.5 mol/L.
[0059] The non-aqueous secondary battery of the present invention
uses the aqueous electrolyte solution having the above composition
and includes at least a positive electrode, a negative electrode,
and a separator.
[0060] For a lithium secondary battery, metal lithium or a lithium
alloy, for example, can be used as the material of the negative
electrode. For a lithium ion secondary battery, a carbon material
that can be doped with lithium ions and de-doped can be used. Such
a carbon material may be graphite or amorphous carbon, and any
carbon materials such as activated carbon, carbon fibers, carbon
black, and mesocarbon microbeads can be used. For a magnesium
secondary battery, examples include metal magnesium and magnesium
alloys.
[0061] Any of transition metal oxides and transition metal sulfides
such as MoS.sub.2, TiS.sub.2, MnO.sub.2, and V.sub.2O.sub.5,
conductive polymers such as polyaniline and polypyrrole, compounds
such as disulfide compounds that can undergo electrolytic
polymerization and depolymerization reversibly, composite oxides of
lithium and transition metals such as LiCoO.sub.2, LiMnO.sub.2,
LiMn.sub.2O.sub.4, LiNiO.sub.2, LiFeO.sub.2, and LiFePO.sub.4, and
composite oxides of magnesium and transition metals can be used as
the material of the positive electrode.
[0062] A fine porous film, for example, is used as the separator.
The thickness of the separator is preferably in the range of 10
.mu.m to 20 .mu.m, and the porosity is preferably in the range of
35% to 50%. Examples of the material of the separator include:
polyolefin-based resins such as polyethylene and polypropylene;
polyester-based resins such as polyethylene terephthalate and
polybutylene terephthalate; and fluorine-based resins such as
polyvinylidene fluoride, a vinylidene fluoride-tetrafluoroethylene
copolymer, a vinylidene fluoride-trifluoroethylene copolymer, and a
vinylidene fluoride-ethylene copolymer.
[0063] The shape, form, and the like of the non-aqueous secondary
battery of the present invention are not especially limited to
particular ones. They may be freely selected from cylindrical,
rectangular, coin, card, large, and other types within the scope of
the present invention.
EXAMPLES
[0064] The present invention will next be described in detail by
way of Examples, but the present invention is not limited to these
Examples.
Example 1
Synthesis of bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl
phosphate
[0065] 340 g of phosphorus trichloride, 184 g of t-butyl alcohol,
and 496 g of 2,2,2-trifluoroethanol were mixed at 0.degree. C., and
the mixture was allowed to react at 60.degree. C. for 3 hours. Then
the resultant mixture was cooled to 0.degree. C., and 193 g of
chlorine gas was blown into the mixture over 6 hours. Next, 9.4 g
of magnesium chloride and 409 g of 2,2,3,3-tetrafluoropropanol were
added to the reaction mixture, and the resultant mixture was
allowed to react at 130.degree. C. for 4 hours. After cooling, 500
g of water and 16 g of sodium hydrogencarbonate were added to the
reaction mixture. The resultant mixture was stirred, and the
aqueous layer was removed. The organic layer was purified by
distillation to obtain 743 g of bis(2,2,2-trifluoroethyl)
2,2,3,3-tetrafluoropropyl phosphate.
[0066] .sup.1H-NMR (400 MHz, CDCl.sub.3) .delta. 5.92 (tt, 1H),
4.39-4.51 (m, 6H)
[0067] .sup.19F-NMR (376 MHz, CDCl.sub.3) .delta. -76.01 (t, 6F),
-125.15 (t, 2F), -137.97 (d, 2F)
[0068] EI-MS m/z 357 [M-F].sup.+, 356 [M-HF].sup.+, 275, 245, 225,
165, 163, 143, 115, 95, 83, 69, 64, 51, 33
Example 2
Synthesis of bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl
phosphate
[0069] 340 g of phosphorus trichloride, 184 g of t-butyl alcohol,
and 660 .mu.g of 2,2,3,3-tetrafluoropropanol were allowed to react
at 0.degree. C., and the resultant mixture was allowed to react at
60.degree. C. for 3 hours. Then the reaction mixture was cooled to
0.degree. C., and 196 g of chlorine gas was blown thereinto over 6
hours. Next, 9.4 g of magnesium chloride and 310 g of
2,2,2-trifluoroethanol were added to the reaction mixture, and the
resultant mixture was allowed to react at 130.degree. C. for 4
hours. After cooling, 500 g of water and 16 g of sodium
hydrogencarbonate were added to the reaction mixture. The resultant
mixture was stirred, and the aqueous layer was removed. The organic
layer was purified by distillation to obtain 765 g of
bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl phosphate.
[0070] EI-MS m/z 389 [M-F].sup.+, 388 [M-HF].sup.+, 307, 277, 257,
227, 195, 163, 155, 143, 115, 95, 83, 69, 64, 51, 33
Example 3
Synthesis of bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl
phosphate
[0071] The same procedure as in Example 1 was repeated except that
244 g of 2,2-difluoroethanol was used instead of 409 g of
2,2,3,3-tetrafluoropropanol to thereby obtain 616 g of
bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate.
[0072] .sup.1H-NMR (400 MHz, CDCl.sub.3) .delta. 5.97 (tt, 1H),
4.38-4.46 (m, 4H), 4.23-4.33 (m, 3H)
[0073] .sup.19F-NMR (376 MHz, CDCl.sub.3) .delta. -75.99 (t, 6F),
-127.67 (dt, 2F)
[0074] EI-MS m/z 307 [M-F].sup.+, 306 (M-HF).sup.+, 275, 263, 245,
225, 207, 165, 163, 143, 115, 83, 69, 64, 51, 33
Example 4
Synthesis of methyl 2,2,3,3-tetrafluoropropyl 2,2,2-trifluoroethyl
phosphate
[0075] 137 g of phosphorus trichloride, 75 g of t-butyl alcohol,
110 g of 2,2,2-trifluoroethanol, and 145 g of
2,2,3,3-tetrafluoropropanol were mixed at 0.degree. C., and the
mixture was allowed to react at 60.degree. C. for 5 hours. Then the
resultant mixture was cooled to 0.degree. C., and 78 g of chlorine
gas was blown into the mixture over 2 hours. Next, 3.8 g of
magnesium chloride and 39 g of methanol were added to the reaction
mixture, and the resultant mixture was allowed to react at
50.degree. C. for 2 hours. After cooling, 281 g of water and 31 g
of sodium hydrogencarbonate were added to the reaction mixture. The
resultant mixture was stirred, and the aqueous layer was removed.
The organic layer was purified by distillation to obtain 55 g of
methyl 2,2,3,3-tetrafluoropropyl 2,2,2-trifluoroethyl
phosphate.
[0076] .sup.1H-NMR (400 MHz, CDCl.sub.3) .delta. 5.94 (tt, 1H),
4.35-4.46 (m, 4H), 3.87 (d, 3H)
[0077] .sup.19F-NMR (376 MHz, CDCl.sub.3) .delta. -76.01 (t, 3F),
-125.58 (td, 2F), -138.44 (d, 2F)
[0078] EI-MS m/z 289 [M-F].sup.+, 288 [M-HF].sup.+, 258, 257, 207,
177, 127, 117, 97, 79, 69, 64, 51, 33
Example 5
Synthesis of bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl
phosphate
[0079] A solution containing 340 g of phosphorus trichloride in 650
g of dichloromethane, a solution containing 184 g of t-butyl
alcohol in 325 g of dichloromethane, and a solution containing 496
of 2,2,2-trifluoroethanol in 325 g of dichloromethane were mixed at
0.degree. C., and the mixture was allowed to react at 60.degree. C.
for 3 hours. Then the resultant mixture was cooled to 0.degree. C.,
and 193 g of chlorine gas was blown into the mixture over 6 hours.
After the solvent was removed under reduced pressure, 9.4 g of
magnesium chloride and 409 g of 2,2,3,3-tetrafluoropropanol were
added to the concentrated solution, and the resultant mixture was
allowed to react at 130.degree. C. for 4 hours. After cooling, 500
g of water and 16 g of sodium hydrogencarbonate were added to the
reaction mixture. The resultant mixture was stirred, and the
aqueous layer was removed. The organic layer was purified by
distillation to obtain 626 g of bis(2,2,2-trifluoroethyl)
2,2,3,3-tetrafluoropropyl phosphate.
Examples 6 to 9 and Comparative Example 1
Physical Properties of Fluorine-Containing Phosphates
[0080] Viscosity (Ubbelohde viscometer, 20.degree. C.) and
permittivity were measured for each of the
bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl phosphate
obtained in Example 1, the bis(2,2,3,3-tetrafluoropropyl)
2,2,2-trifluoroethyl phosphate obtained in Example 2, the
bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate obtained in
Example 3, the methyl 2,2,3,3-tetrafluoropropyl
2,2,2-trifluoroethyl phosphate obtained in Example 4, and
tris(2,2,3,3-tetrafluoropropyl) phosphate used as a comparative
fluorine-containing phosphate. The results are shown in Table
1.
[0081] The bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl
phosphate, bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl
phosphate, bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate,
and methyl 2,2,3,3-tetrafluoropropyl 2,2,2-trifluoroethyl phosphate
of the present invention were found to have improved viscosity and
permittivity as compared to those of the
tris(2,2,3,3-tetrafluoropropyl) phosphate.
TABLE-US-00001 TABLE 1 VISCO- SITY FLUORINE-CONTAINING 20.degree.
C. PERMIT- PHOSPHATE (mPa s) TIVITY Example 6
BIS(2,2,2-TRIFLUOROETHYL) 10.2 9.9 2,2,3,3-TETRAFLUOROPROPYL
PHOSPHATE Example 7 BIS(2,2,3,3- 22.6 9.3 TETRAFLUOROPROPYL)
2,2,2-TRIFLUOROETHYL PHOSPHATE Example 8 BIS(2,2,2-TRIFLUOROETHYL)
7.2 33.8 2,2-DIFLUOROETHYL PHOSPHATE Example 9 METHYL 2,2,3,3- 9.6
80.4 TETRAFLUOROPROPYL 2,2,2-TRIFLUOROETHYL PHOSPHATE Comparative
TRIS(2,2,3,3- 50.1 8.6 Example 1 TETRAFLUOROPROPYL) PHOSPHATE
Examples 10 to 12 and Comparative Examples 2 and 3
Ability of Fluorine-Containing Phosphate to Dissolve
Electrolyte
[0082] LiPF.sub.6 was added at 20.degree. C. to each of the
bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl phosphate,
bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl phosphate,
bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate, methyl
2,2,3,3-tetrafluoropropyl 2,2,2-trifluoroethyl phosphate, and
comparative fluorine-containing phosphates, i.e.,
tris(2,2,3,3-tetrafluoropropyl) phosphate and
tris(2,2,2-trifluoroethyl) phosphate. Each mixture was stirred at
20.degree. C. for 6 hours to dissolve LiPF.sub.6. Undissolved
LiPF.sub.6 was separated by filtration, and the ability to dissolve
LiPF.sub.6 was determined by .sup.19F-NMR analysis of the solution.
The results are shown in Table 2.
[0083] Each of the low-symmetric and asymmetric fluorine-containing
phosphates of the present invention was found to have a
significantly improved ability to dissolve the electrolyte as
compared to those of the symmetric fluorine-containing
phosphates.
TABLE-US-00002 TABLE 2 ABILITY TO DISSOLVE FLUORINE-CONTAINING
LiPF6 PHOSPHATE (g/100 g) Example 10 BIS(2,2,2-TRIFLUOROETHYL) 6.8
2,2,3,3-TETRAFLUOROPROPYL PHOSPHATE Example 11
BIS(2,2,2-TRIFLUOROETHYL) 10.0 2,2-DIFLUOROETHYL PHOSPHATE Example
12 METHYL 2,2,3,3- 15.6 TETRAFLUOROPROPYL 2,2,2-TRIFLUOROETHYL
PHOSPHATE Comparative TRIS (2,2,3,3-TETRAFLUOROPROPYL) 3.8 Example
2 PHOSPHATE Comparative TRIS(2,2,2-TRIFLUOROETHYL) 5.3 Example 3
PHOSPHATE
Examples 13 to 17 and Comparative Examples 4 and 5
Flame Retardant Performance of Fluorine-Containing Phosphates
[0084] The bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl
phosphate was added in an amount of 20 percent by weight to a
solution mixture containing ethylene carbonate, dimethyl carbonate,
and ethyl methyl carbonate in a volume ratio of 1:1:1. Then
LiPF.sub.6 was dissolved in the resultant mixture in a ratio of 1
mol/L, and the mixture was referred to as a non-aqueous electrolyte
solution a.
[0085] The bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl
phosphate was added in an amount of 10 percent by weight to a
solution mixture containing ethylene carbonate, dimethyl carbonate,
and ethyl methyl carbonate in a volume ratio of 1:1:1. Then
LiPF.sub.6 was dissolved in the resultant mixture in a ratio of 1
mol/L, and the mixture was referred to as a non-aqueous electrolyte
solution b.
[0086] The bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl
phosphate was added in an amount of 20 percent by weight to a
solution mixture containing ethylene carbonate, dimethyl carbonate,
and ethyl methyl carbonate in a volume ratio of 1:1:1. Then
LiPF.sub.6 was dissolved in the resultant mixture in a ratio of 1
mol/L, and the mixture was referred to as a non-aqueous electrolyte
solution c.
[0087] The bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate
was added in an amount of 20 percent by weight to a solution
mixture containing ethylene carbonate, dimethyl carbonate, and
ethyl methyl carbonate in a volume ratio of 1:1:1. Then LiPF.sub.6
was dissolved in the resultant mixture in a ratio of 1 mol/L, and
the mixture was referred to as a non-aqueous electrolyte solution
d.
[0088] The methyl 2,2,3,3-tetrafluoropropyl 2,2,2-trifluoroethyl
phosphate was added in an amount of 20 percent by weight to a
solution mixture containing ethylene carbonate, dimethyl carbonate,
and ethyl methyl carbonate in a volume ratio of 1:1:1. Then
LiPF.sub.6 was dissolved in the resultant mixture in a ratio of 1
mol/L, and the mixture was referred to as a non-aqueous electrolyte
solution e.
[0089] dimethyl 2,2,2-trifluoroethyl phosphate was added in an
amount of 20 percent by weight to a solution mixture containing
ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate
in a volume ratio of 1:1:1. Then LiPF.sub.6 was dissolved in the
resultant mixture in a ratio of 1 mol/L, and the mixture was
referred to as a non-aqueous electrolyte solution f.
[0090] trimethyl phosphate was added in an amount of 20 percent by
weight to a solution mixture containing ethylene carbonate,
dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of
1:1:1. Then LiPF.sub.6 was dissolved in the resultant mixture in a
ratio of 1 mol/L, and the mixture was referred to as a non-aqueous
electrolyte solution g. Test pieces were prepared by impregnating
glass filters with the respective electrolytes. Each test piece was
subjected to a test flame for 10 seconds. After the test flame was
moved away, the manner of combustion was visually observed. The
results are shown in Table 3. For each of the non-aqueous
electrolyte solutions containing any of the
bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl phosphate,
bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl phosphate,
bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate, and methyl
2,2,3,3-tetrafluoropropyl 2,2,2-trifluoroethyl phosphate of the
present invention each containing fluorine in an amount of 30
percent by weight or more, the test piece was not combusted.
However, for each of the non-aqueous electrolyte solutions
containing any of the dimethyl 2,2,2-trifluoroethyl phosphate and
trimethyl phosphate each containing fluorine in an amount of less
than 30 percent by weight, the test piece was combusted.
TABLE-US-00003 TABLE 3 RATIO OF FLUORINE AMOUNT OF ATOMS FLUORINE-
NON- CONTAINED CONTAINING AQUEOUS IN FLUORINE- PHOSPHATE
ELECTROLYTE CONTAINING ADDED COMBUSTIBILITY SOLUTION
FLUORINE-CONTAINING PHOSPHATE PHOSPHATE (wt %) (wt %) Example 13 a
BIS(2,2,2-TRIFLUOROETHYL) 50.5 20 NOT 2,2,3,3-TETRAFLUOROPROPYL
COMBUSTED PHOSPHATE Example 14 b BIS(2,2,2-TRIFLUOROETHYL) 50.5 10
NOT 2,2,3,3-TETRAFLUOROPROPYL COMBUSTED PHOSPHATE Example 15 c
BIS(2,2,3,3-TETRAFLUOROPROPYL) 51.2 20 NOT 2,2,2-TRIFLUOROETHYL
PHOSPHATE COMBUSTED Example 16 d BIS(2,2,2-TRIFLUOROETHYL) 46.6 20
NOT 2,2-DIFLUOROETHYL PHOSPHATE COMBUSTED Example 17 e METHYL
2,2,3,3- 43.2 20 NOT TETRAFLUOROPROPYL COMBUSTED
2,2,2-TRIFLUOROETHYL PHOSPHATE Comparative f DIMETHYL
2,2,2-TRIFLUOROETHYL 27.4 20 COMBUSTED Example 4 PHOSPHATE
Comparative g TRIMETHYL PHOSPHATE 0 20 COMBUSTED Example 5
Examples 18 to 26 and Comparative Examples 6 to 8
Evaluation of Battery Performance of Non-Aqueous Secondary
Batteries Containing Fluorine-Containing Phosphates
[0091] Non-aqueous secondary batteries as shown in the
cross-sectional view in FIG. 1 were produced. More specifically,
the negative electrode 1 (with a thickness of 0.1 mm) was obtained
by coating a current collector 2 made of copper foil with a mixture
of graphite, polyvinylidene fluoride, and N-methyl-2-pyrrolidone,
drying the coating, and subjecting the product to pressure molding.
The positive electrode 3 (with a thickness of 0.1 mm) was obtained
by coating a current collector 4 made of copper foil with a mixture
of LiCoO.sub.2, acetylene black, and N-methyl-2-pyrrolidone, drying
the coating, and subjecting the product to pressure molding. The
materials constituting the negative electrode 1 and the positive
electrode 3 were stacked with a porous polyethylene separator 5
(with a thickness of 16 .mu.m and a porosity of 50%) interposed
therebetween. The bis(2,2,2-trifluoroethyl)
2,2,3,3-tetrafluoropropyl phosphate was mixed in a weight ratio of
20% with a solvent mixture containing ethylene carbonate, dimethyl
carbonate, and methyl ethyl carbonate in a volume ratio of 1:1:1 to
thereby prepare a solvent. Then LiPF.sub.6 was dissolved in the
prepared solvent in a ratio of 1.0 mol/L, and the obtained solution
was used as the non-aqueous electrolyte solution of the
above-described battery. The material between the positive and
negative electrodes was impregnated with the prepared non-aqueous
electrolyte solution, and a metal-resin composite film 6 was
thermally bonded to seal the product. The obtained non-aqueous
secondary battery is referred to as A1.
[0092] The bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl
phosphate was mixed in a weight ratio of 10% with a solvent mixture
containing ethylene carbonate, dimethyl carbonate, and methyl ethyl
carbonate in a volume ratio of 1:1:1 to thereby prepare a solvent.
Then LiPF.sub.6 was dissolved in the prepared solvent in a ratio of
1.0 mol/L, and the obtained solution was used as a non-aqueous
electrolyte solution. After impregnation with the prepared
non-aqueous electrolyte solution, the product was sealed. The
obtained non-aqueous secondary battery is referred to as A2.
[0093] The bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl
phosphate was mixed in a weight ratio of 30% with a solvent mixture
containing ethylene carbonate, dimethyl carbonate, and methyl ethyl
carbonate in a volume ratio of 1:1:1 to thereby prepare a solvent.
Then LiPF.sub.6 was dissolved in the prepared solvent in a ratio of
1.0 mol/L, and the obtained solution was used as a non-aqueous
electrolyte solution. After impregnation with the prepared
non-aqueous electrolyte solution, the product was sealed. The
obtained non-aqueous secondary battery is referred to as A3.
[0094] The bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl
phosphate was mixed in a weight ratio of 50% with a solvent mixture
containing ethylene carbonate, dimethyl carbonate, and methyl ethyl
carbonate in a volume ratio of 1:1:1 to thereby prepare a solvent.
Then LiPF.sub.6 was dissolved in the prepared solvent in a ratio of
1.0 mol/L, and the obtained solution was used as anon-aqueous
electrolyte solution. After impregnation with the prepared
non-aqueous electrolyte solution, the product was sealed. The
obtained non-aqueous secondary battery is referred to as A4.
[0095] The bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl
phosphate was mixed in a weight ratio of 30% with a solvent mixture
containing ethylene carbonate and
2,2,3,3-tetrafluoropropyl-1,1,2,2-tetrafluoroethyl ether in a
volume ratio of 2:1 to thereby prepare a solvent. Then LiPF.sub.6
was dissolved in the prepared solvent in a ratio of 1.0 mol/L, and
the obtained solution was used as a non-aqueous electrolyte
solution. After impregnation with the prepared non-aqueous
electrolyte solution, the product was sealed. The obtained
non-aqueous secondary battery is referred to as A5.
[0096] The bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl
phosphate was mixed in a weight ratio of 20% with a solvent mixture
containing ethylene carbonate, dimethyl carbonate, and methyl ethyl
carbonate in a volume ratio of 1:1:1 to thereby prepare a solvent.
Then LiPF.sub.6 was dissolved in the prepared solvent in a ratio of
1.0 mol/L, and the obtained solution was used as anon-aqueous
electrolyte solution. After impregnation with the prepared
non-aqueous electrolyte solution, the product was sealed. The
obtained non-aqueous secondary battery is referred to as B.
[0097] The bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate
was mixed in a weight ratio of 20% with a solvent mixture
containing ethylene carbonate, dimethyl carbonate, and methyl ethyl
carbonate in a volume ratio of 1:1:1 to thereby prepare a solvent.
Then LiPF.sub.6 was dissolved in the prepared solvent in a ratio of
1.0 mol/L, and the obtained solution was used as a non-aqueous
electrolyte solution. After impregnation with the prepared
non-aqueous electrolyte solution, the product was sealed. The
obtained non-aqueous secondary battery is referred to as C1.
[0098] The bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate
was mixed in a weight ratio of 30% with a solvent mixture
containing ethylene carbonate and
2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether in a volume
ratio of 2:1 to thereby prepare a solvent. Then LiPF.sub.6 was
dissolved in the prepared solvent in a ratio of 1.0 mol/L, and the
obtained solution was used as a non-aqueous electrolyte solution.
After impregnation with the prepared non-aqueous electrolyte
solution, the product was sealed. The obtained non-aqueous
secondary battery is referred to as C2.
[0099] The methyl 2,2,3,3-tetrafluoropropyl 2,2,2-trifluoroethyl
phosphate was mixed in a weight ratio of 20% with a solvent mixture
containing ethylene carbonate, dimethyl carbonate, and methyl ethyl
carbonate in a volume ratio of 1:1:1 to thereby prepare a solvent.
Then LiPF.sub.6 was dissolved in the prepared solvent in a ratio of
1.0 mol/L, and the obtained solution was used as anon-aqueous
electrolyte solution. After impregnation with the prepared
non-aqueous electrolyte solution, the product was sealed. The
obtained non-aqueous secondary battery is referred to as D.
[0100] tris(2,2,2-trifluoroethyl) phosphate was mixed in a weight
ratio of 20% with a solvent mixture containing ethylene carbonate,
dimethyl carbonate, and methyl ethyl carbonate in a volume ratio of
1:1:1 to thereby prepare a solvent. Then LiPF.sub.6 was dissolved
in the prepared solvent in a ratio of 1.0 mol/L, and the obtained
solution was used as a non-aqueous electrolyte solution. After
impregnation with the prepared non-aqueous electrolyte solution,
the product was sealed. The obtained non-aqueous secondary battery
is referred to as E.
[0101] tris(2,2,3,3-tetrafluoropropyl) phosphate was mixed in a
weight ratio of 20% with a solvent mixture containing ethylene
carbonate, dimethylcarbonate, and methylethylcarbonate in a volume
ratio of 1:1:1 to thereby prepare a solvent. Then LiPF.sub.6 was
dissolved in the prepared solvent in a ratio of 1.0 mol/L, and the
obtained solution was used as a non-aqueous electrolyte solution.
After impregnation with the prepared non-aqueous electrolyte
solution, the product was sealed. The obtained non-aqueous
secondary battery is referred to as F1.
[0102] tris(2,2,3,3-tetrafluoropropyl) phosphate was mixed in a
weight ratio of 30% with a solvent mixture containing ethylene
carbonate and 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether
in a volume ratio of 1:1 to thereby prepare a solvent. To prepare a
non-aqueous electrolyte solution, LiPF.sub.6 was dissolved in the
prepared solvent in a ratio of 1.0 mol/L. However, the LiPF.sub.6
was not dissolved, and a large amount of precipitates were formed.
The ability of such a symmetric fluorine-containing phosphate to
dissolve LiPF.sub.6 is not sufficient. Therefore, when the
low-flash point chain carbonates used as low-viscosity solvents
were replaced with the nonflammable fluorine-containing ether to
further improve safety, it was difficult to prepare an electrolyte
solution.
[0103] The initial discharge capacity and high-rate discharge
capacity of each of the non-aqueous secondary batteries A1, A2, A3,
A4, A5, B, C1, C2, and D of the present invention and the
comparative non-aqueous secondary batteries E and F1 were measured.
The initial discharge capacity was determined by performing
constant-voltage and constant-current charge with a current of 10
mA and a final voltage of 4.2 V at 20.degree. C. and then
performing constant-current discharge with a current of 2 mA and a
final voltage of 2.7 V at 20.degree. C. The high-rate discharge
capacity was determined by per forming constant-voltage and
constant-current charge with a current of 10 mA and a final voltage
of 4.2 V at 20.degree. C. and then performing constant-current
discharge with a current of 30 mA and a final voltage of 2.7 Vat
20.degree. C. The results are shown in Table 4. Each non-aqueous
secondary battery of the present invention containing a
fluorine-containing phosphate having a specific structure in the
electrolyte solution exhibited a high high-rate discharge
capacity.
TABLE-US-00004 TABLE 4 INITIAL HIGH-RATE NON-AQUEOUS AMOUNT
DISCHARGE DISCHARGE SECONDARY MIXED CAPACITY CAPACITY BATTERY
FLUORINE-CONTAINING PHOSPHATE (wt %) SOLVENT (mAh) (mAh) Example 18
A1 BIS(2,2,2-TRIFLUOROETHYL) 20 EC-DMC-EMC 9.8 7.7
2,2,3,3-TETRAFLUOROPROPYL (1:1:1) PHOSPHATE Example 19 A2
BIS(2,2,2-TRIFLUOROETHYL) 10 EC-DMC-EMC 9.9 7.9
2,2,3,3-TETRAFLUOROPROPYL (1:1:1) PHOSPHATE Example 20 A3
BIS(2,2,2-TRIFLUOROETHYL) 30 EC-DMC-EMC 9.6 7.5
2,2,3,3-TETRAFLUOROPROPYL (1:1:1) PHOSPHATE Example 21 A4
BIS(2,2,2-TRIFLUOROETHYL) 50 EC-DMC-EMC 9.3 7.0
2,2,3,3-TETRAFLUOROPROPYL (1:1:1) PHOSPHATE Example 22 A5
BIS(2,2,2-TRIFLUOROETHYL) 30 EC-TFPTFEE 9.3 6.9
2,2,3,3-TETRAFLUOROPROPYL (2:1) PHOSPHATE Example 23 B
BIS(2,2,3,3-TETRAFLUOROPROPYL) 20 EC-DMC-EMC 9.6 7.4
2,2,2-TRIFLUOROETHYL PHOSPHAE (1:1:1) Example 24 C1
BIS(2,2,2-TRIFLUOROETHYL) 20 EC-DMC-EMC 9.9 7.9 2,2-DIFLUOROETHYL
PHOSPHATE (1:1:1) Example 25 C2 BIS(2,2,2-TRIFLUOROETHYL) 30
EC-TFETFEE 9.5 7.1 2,2-DIFLUOROETHYL PHOSPHAE (2:1) Example 26 D
METHYL 2,2,3,3-TETRAFLUOROPROPYL 20 EC-DMC-EMC 9.8 7.9
2,2,2-TRIFLUOROETHYL PHOSPHATE (1:1:1) Comparative E
TRIS(2,2,2-TRIFLUOROETHYL) 20 EC-DMC-EMC 9.5 6.9 Example 6
PHOSPHATE (1:1:1) Comparative F1 TRIS(2,2,3,3-TETRAFLUOROPROPYL) 20
EC-DMC-EMC 9.4 6.7 Example 7 PHOSPHATE (1:1:1) Comparative F2
TRIS(2,2,3,3-TETRAFLUOROPROPYL) 30 EC-TFETFEE LiPF6 PRECIPITATED
Example 8 PHOSPHATE (2:1) TFPTFEE:
2,2,3,3-TETRAFLUOROPROPYL-1,1,2,2-TETRAFLUOROETHYL ETHER TFETFEE:
2,2,2-TRIFLUOROETHYL-1,1,2,2-TETRAFLUOROETHYL ETHER
[0104] The non-aqueous secondary battery C1 of the present
invention and the comparative non-aqueous secondary battery E were
subjected to a battery cycle life test. More specifically,
constant-voltage and constant-current charge with a current of 2 mA
and a final voltage of 4.2 V and constant-current discharge with a
current of 2 mA and a final voltage of 2.7 were repeated 200
times.
[0105] For the non-aqueous secondary battery C of the present
invention, the ratio of the 200th discharge capacity to the initial
discharge capacity (capacity retention) was 94%.
[0106] For the comparative non-aqueous secondary battery F, the
ratio of the 200th discharge capacity to the initial discharge
capacity (capacity retention) was 89%.
[0107] These results showed that the non-aqueous secondary battery
of the present invention had not only high high-rate
charge-discharge characteristics but also an improved and favorable
cycle life.
INDUSTRIAL APPLICABILITY
[0108] The addition of the fluorine-containing phosphate having a
specific structure of the present invention to a non-aqueous
electrolyte solution allows a non-aqueous secondary battery having
improved battery characteristics such as high-rate charge-discharge
characteristics to be obtained, and this is very useful.
REFERENCE SIGNS LIST
[0109] 1: negative electrode [0110] 2: current collector [0111] 3:
positive electrode [0112] 4: current collector [0113] 5: porous
polyethylene separator [0114] 6: metal-resin composite film [0115]
7: positive electrode terminal [0116] 8: negative electrode
terminal
* * * * *